R-T-B-BASED RARE EARTH PERMANENT MAGNET

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An R-T-B-based rare earth permanent magnet in which the composition formula is represented by (R11-x-ySmxR2y)aTbBcMd, wherein : R1 is one or more rare earth elements not including Sm or Y; R2 is one or more rare earth elements from among Y, Ce, and La; T is Fe, etc.; M is Ga, etc.; x and y are in the region indicated in fig. 1; the relationships 0.16 ≤ a/b ≤ 0.28, 0.050 ≤ c/b ≤ 0.075, and 0.005 ≤ d/b ≤ 0.028 are satisfied; the R-T-B-based rare earth permanent magnet includes a grain boundary phase and a main phase comprising an R2T14B compound; the average crystal grain diameter of the main-phase crystal particles is D50 ≤ 4.00 μm; the granularity distribution is (D90-D10)/D50 ≤ 1.60; and the coverage of the grain boundary phase is at least 70.0%.